This invention relates to water spray sprinklers and nozzles for fire protection service, and, in particular, to those nozzles in which a single stream of water is discharged and impacts or impinges against a downstream element as a means of deflecting, spreading or diffusing the discharge stream into a spray pattern consisting of individual droplets.
Water sprays consisting of relatively small water droplets have been shown to be among the most efficient fire extinguishing media currently available. Small water droplets suspended in the atmosphere can be forcibly injected or entrained through the convective currents, into the combustion region of a fire, where they quickly evaporate. The evaporation of these droplets has an impact upon the combustion process by absorbing some quantity of the energy output of the fire, and by displacing gaseous oxidizing agents. At some critical point, then the fire is no longer capable of self-sustained combustion, it is extinguished. It has been shown that droplets of less than 50 microns in size are extremely efficient fire extinguishing agents. As droplet size increases, the efficiency of the fire extinguishing media, typically water, decreases, although it has been demonstrated that water sprays with the majority of the droplets between 50 and 250 microns in size can be highly effective and efficient fire extinguishing agents, particularly when delivered in a componentized spray pattern. Fischer U.S. Pat. No. 5,839,667 teaches that it can be desirable to selectively provide areas of higher water discharge per unit area, greater droplet size, and/or greater droplet momentum. It has also been shown that different expected fire scenarios may require different spray pattern characteristics, if the effectiveness of fixed fire fighting system is to be maximized.
The main types of water mist nozzles for fire protection include diffuser impingement nozzles, pressure jet nozzles, and gas atomizing nozzles. Diffuser impingement nozzles operate by impacting a coherent water stream against a diffuser. The diffuser breaks the stream into a predetermined distribution of mist. Diffuser impingement-type water mist nozzles are described in Fischer U.S. Pat. No. 5,392,993 and in Fischer U.S. Pat. No. 5,505,383. Pressure jet nozzles function by discharging high velocity water streams through small orifices with an internal shape, e.g., a scroll-type arrangement is typical, designed to break up the water stream. A pressure jet type water mist nozzle is described in Sundholm U.S. Pat. No. 5,513,709. Gas-atomizing water mist nozzles operate by mixing compressed gas with water in a mixing chamber at the nozzle discharge orifice. A gas atomizing water mist nozzle is described in Loepsinger U.S. Pat. No. 2,361,144.
The spray pattern characteristics produced by existing diffuser elements utilized in impingement-type water mist nozzles fall into two distinct categories. The first category is a relatively uniformly filled, umbrella-shaped cone of spray extending from the discharge nozzle. The second category is a largely hollow cone, with the spray pattern forming a uniform or nonuniform shell of spray. Fischer U.S. Pat. No. 5,829,684 describes a nozzle producing a combination of these two fundamental types, with a uniform, umbrella-shaped shell superimposed over a relatively uniformly filled inner cone.
According to one aspect of the invention, an upright-type fire protection spray mist nozzle comprises a base defining an orifice, with an orifice axis, through which fire-retardant fluid can flow, an inlet section having an upstream end and defining a conduit for flow of fire-retardant fluid along the orifice axis and leading to an upstream end of the orifice, and a diffuser element positioned coaxially downstream of the orifice, the diffuser element defining an impingement surface that is at least substantially imperforate in the axial direction and positioned for impingement by a stream of fire-retardant fluid flowing from the orifice in a stream direction along the orifice axis. The impingement surface comprises a central conical shape surface region extending generally toward the orifice, with an apex portion disposed along the orifice axis, a peripheral edge disposed generally radially outward from the conical shape surface region, and a concave, toroidal surface region generally between the conical shape surface region and the peripheral edge.
Preferred embodiments of this aspect of the invention may include one or more of the following additional features. The apex and the peripheral edge are disposed in a plane generally perpendicular to the orifice axis. Preferably, at least a portion of the toroidal surface region is recessed downstream from the plane of the apex and the peripheral edge, relative to the orifice. More preferably, the toroidal surface region is recessed downstream from the plane of the apex and the peripheral edge, relative to the orifice. The stream of fire retardant fluid flowing from the orifice to impinge upon the impingement surface is substantially steady and coherent. The concave, toroidal surface region has a shape formed by rotation of an ellipse having a major diameter greater than the radius of the peripheral edge of the impingement surface, rotated about a line defined by the orifice axis passing through the apex. The impingement surface defines at least one surface discontinuity in a region of the peripheral edge for redirecting a portion of the flow of fire retardant fluid along the impingement surface. Preferably, the impingement surface defines a set of surface discontinuities spaced circumferentially about the orifice axis in the region of the peripheral edge for redirecting a portion of the flow of fire retardant fluid along the impingement surface. More preferably, redirecting a portion of the flow of fire retardant fluid by the set of surface discontinuities divides the flow into multiple segments at the peripheral edge with little loss of energy. The surface discontinuity has the form of a notch in the impingement surface. Preferably, the notch defines a surface region extending to the peripheral edge in a plane generally tangent to a base region of the concave surface and lying generally perpendicular to the orifice axis. The stream has a diameter, and the ratio of the diameter of a region of the concave surface lying generally tangent to a plane that is generally perpendicular to the orifice axis and the diameter of the stream of fire retardant fluid flowing from the orifice and intersecting the impingement surface is greater than or equal to 2. The upright-type fire protection spray mist nozzle may be in the form of an open nozzle for use in deluge-type fire protection systems, or, alternatively, may be in the form of an automatically-operating nozzle comprising, in a standby condition, a releasable orifice seal secured in position by a thermally-responsive element.
According to another aspect of the invention, an upright-type fire protection spray mist nozzle comprises a base defining an orifice, with an orifice axis, through which fire-retardant fluid can flow, an inlet section having an upstream end and defining a conduit for flow of fire-retardant fluid along the orifice axis and leading to an upstream end of the orifice, and a diffuser element positioned coaxially downstream of the orifice, the diffuser element defining an impingement surface that is at least substantially imperforate in the axial direction and positioned for impingement by a stream of fire-retardant fluid flowing from the orifice in a stream direction along the orifice axis. The impingement surface is shaped to divert fire-retardant fluid in the stream to flow from the orifice axis radially outward, along the impingement surface, toward a peripheral edge of the impingement surface, the impingement surface adapted to substantially redirect the flow of fire-retardant fluid from the stream by at least 90xc2x0 from the stream direction while maintaining the flow of fire-retardant fluid toward the peripheral edge substantially in contact with the impingement surface in a manner to substantially avoid splashing.
Preferred embodiments of this aspect of the invention may include the following additional feature. The impingement surface is adapted to redirect the flow of fire-retardant fluid by at least 110xc2x0 from the stream direction while maintaining the flow of fire-retardant fluid toward the peripheral edge substantially in contact with the impingement surface in a manner to substantially avoid splashing.
According to still another aspect of the invention, an upright-type fire protection spray mist nozzle comprises a base defining an orifice, with an orifice axis, through which fire-retardant fluid can flow, an inlet section having an upstream end and defining a conduit for flow of fire-retardant fluid along the orifice axis and leading to an upstream end of the orifice, and a diffuser element positioned coaxially downstream of the orifice. The diffuser element defines an impingement surface that is at least substantially imperforate in the axial direction and positioned for impingement by a stream of fire-retardant fluid flowing from the orifice in a stream direction along the orifice axis, the impingement surface comprising a central conical shape surface region extending generally toward the orifice, with an apex portion disposed along the orifice axis, a peripheral edge disposed generally radially outward from the conical shape surface region, and a concave, toroidal surface region generally between the conical shape surface region and the peripheral edge, the impingement surface being shaped to divert the fire-retardant fluid in the stream to flow from the orifice axis radially outward, along the impingement surface, towards the peripheral edge of the impingement surface, the impingement surface being adapted to redirect the flow of fire-retardant fluid from the stream by at least 90xc2x0 from the stream direction while maintaining the flow of fire-retardant fluid toward the peripheral edge substantially in contact with the impingement surface in a manner to substantially avoid splashing.
According to another aspect of the invention, an upright-type fire protection spray mist nozzle comprises a base defining an orifice, with an orifice axis, through which fire-retardant fluid can flow, an inlet section having an upstream end and defining a conduit for flow of fire-retardant fluid along the orifice axis and leading to an upstream end of the orifice, and a diffuser element defining an impingement surface that is at least substantially imperforate in an axial direction and positioned for impingement by a stream of fire-retardant fluid flowing from the orifice in a stream direction along the orifice axis, the diffuser element being positioned generally above a horizontal plane through a downstream end of the orifice.
According to another aspect of the invention, an upright-type fire protection spray mist nozzle discharges a spray of fire-retardant fluid over an area to be protected from fire, the spray being characterized by a Dv90 droplet size diameter of less than about 250 microns, preferably less than about 200 microns, and more preferably less than about 150 microns, when measured at a pressure of a 175 psi at the inlet to the nozzle, in accordance with the procedure recommended in the 2000 edition of the NFPA 750 Standard on Water Mist Fire Protection Systems (also see Section 1-4.5 for the definition of xe2x80x9cDv90 droplet size diameterxe2x80x9d).
According to still another aspect of the invention, an upright-type fire protection spray mist nozzle comprises a base defining an orifice, with an orifice axis, through which fire-retardant fluid can flow; and an inlet section having an upstream end and defining a conduit for flow of fire-retardant fluid along the orifice axis and leading to an upstream end of the orifice. A diffuser element defines all impingement surface that is at least substantially imperforate in the axial direction and positioned for impingement by a stream of fire-retardant fluid flowing from the orifice in a stream direction along the orifice axis, the diffuser element being positioned generally above a horizontal plane through a downstream end of orifice, and the orifice has an orifice diameter preferably less than about 0.200 inch, and more preferably less than about 0.150 inch, and still more preferably less than 0.100 inch.
The invention provides, in its broadest aspect, an upright-type fire protection spray mist nozzle, and further provides a diffuser for an impingement-type nozzle having a solid (i.e., at least substantially imperforate in an axial direction), three-dimensional surface shaped to receive and redirect a coherent fluid stream impinged thereupon with substantially no splashing, even when the primary axis of the fluid stream at impact is essentially completely opposed by the impingement surface. Furthermore, surface discontinuities defined by the impingement surface discretely divide the impinging fluid stream into multiple segments with little energy loss, even at low velocities, and selected segments can essentially reversed in direction with respect to the initial stream flow direction from the nozzle outlet. Additionally, the resulting spray pattern discharge consists of water droplets that appear to be substantially smaller than those typically associated with impingement-type diffusers, even those with smaller orifices. For example, with a fluid (water) pressure of about 175 psi at the inlet section of the mist nozzle of this invention having an orifice diameter of about 0.130 inch, the nozzle discharges a spray with a Dv90 droplet size diameter of less than 200 microns, as compared to a Dv90 droplet size diameter of the order of 300 microns for the Grinnell Type AM4 AquaMist(copyright) pendent-type nozzle having a nominal orifice diameter of 0.091 inch, as described in Grinnell Technical Data Sheet TD1173, when measured in accordance with the procedure recommended in the 2000 Edition of the NFPA 750 Standard on Water Mist Fire Protection Systems.
The required spray pattern characteristics of mist nozzles, including droplet size and droplet count density, for use in fixed spray fire fighting systems are determined by the expected fire scenario. Of particular interest is redirection of a majority of the discharged water downstream of the impingement surface of the diffuser in a direction nominally opposite to the direction of bulk flow of the water stream, upstream of the impingement surface of the diffuser, while maintaining relatively small droplet size within the nozzle spray pattern. The attribute of maintaining small droplet size while reversing the bulk average direction of the fluid flow allows spray pattern characteristics not previously achieved using existing technology.
The present invention provides a nozzle that can be employed to distribute a water mist discharge pattern that is discretely adjustable, allowing predetermined positioning of a multitude of areas of high and low water discharge density as deemed preferable for an expected fire scenario. The result is an improvement in performance over existing impingement-type water mist diffusers.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.